There are increasing numbers of modern electronic apparatuses using touch panels or touch screens as their main input/output (I/O) devices. These touch panels/screens are capable for detecting fingers as well as pen-shaped devices (i.e. styli). Styli allow more accurate input of positions since they are typically thinner than fingers.
Some applications require the use of another kind of input device, joysticks, such as computer-aided design (CAD) software, flight simulation games or other types of games. For flight simulation games, joysticks can be used to control two axes: roll and pitch, and with the cooperation of another input device such as a keyboard or a touch panel, yaw and throttle can also be controlled. As such, the motions of an airplane in three dimensional space can be completely simulated.
FIG. 1 shows FIG. 7 of U.S. Pat. No. 6,429,849, which is a schematic diagram depicting a conventional joystick. It can be seen that there are complicated mechanics underneath a joystick handle 123 for determining and outputting angular displacements about X, Y and Z axes. Accordingly, an axial direction and a tilt angle of the joystick handle 123 can be derived. For convenience, when the handle 123 is positioned in the center with no force applied, the angular displacements about the X, Y and Z axes are all zero. Meanwhile, the handle 123 is parallel to the Z axis and perpendicular to the XY plane.
When the handle 123 experiences a force and moves in a direction indicated by F, there is an angular displacement about the X axis. When the handle 123 experiences a force and moves in direction indicated by L, there is an angular displacement about the Y axis. When the angular displacement of at least one of X and Y axes is not zero, the handle 123 will have a tilt angle and an axial direction with respect to the XY plane. In other words, the angular displacements about the X and Y axes can be converted into a tilt angle and an axial direction of the handle 123. On the contrary, if a tilt angle and an axial direction of the handle 123 are known, then the angular displacements about the X and Y axes can be calculated.
It can be seen from FIG. 1, conventional joysticks are often equipped with a large amount of components. As there are a considerable amount of movable parts, conventional joysticks may be easily broken. This is even more so if the joysticks are not used with care. Moreover, the prices of these joysticks are relatively low, which increases the probability of being thrown away once they are broken. Therefore, there is a need for a touch sensitive system that allows a stylus to be used as a joystick, such that users only need one type of device to achieve multiple types of control methods and input experiences.